class_docstr: A tool to enforce non-reentrancy.
  Mostly used on DataFlow whose :meth:`get_data` is stateful,
  so that multiple instances of the iterator cannot co-exist.
code: def __init__(self):
      self._lock = threading.Lock()
  
imports: import threading
  from abc import ABCMeta, abstractmethod
  import six
  from ..utils.utils import get_rng
label_desc: Use image node_id 1 to create a new DataFlowReentrantGuard object from inherited base classes: object with example: obj = DataFlowReentrantGuard()